The advantage of DDEC is that you get an electronically controlled engine, with better fuel economy and lower emissions, which is why they went that route. It's entirely appropriate in the context of a new, professionally maintained fleet of for-profit coaches where the added cost of acquisition and maintenance can be leveraged over better performance over hundreds of thousands of miles. The advantage of the MUI mechanical governor is that they are easy to work on, anyone with a book, some tools and some patience can do a tune up, they don't even need electricity to run (start, mostly yes, run - no) and they do a decent job of producing efficient power. Usually the question is moot - you take what is in your bus and if you want a modern-ish (post 1990 or so) vehicle or engine you get electronic controlled engines. My choice is easy - I have mechanical, I at least have a hope of fixing it if it breaks. No chance with a DDEC, it's swap the module, and hope you can get one programmed for your engine and that it actually works when and if it shows up.

Vanilla or chocolate both are ok but you really need a ATEC controlled transmission when using a automatic to get the full benefits of the DDEC for any type fuel saving then you need the Pro/Link with software for both $$$$.$$

The GM with all the ground problems they have from time to time I think I would stay with a mechanical around 300 hp to control the heat

DDEC sounds great on paper and you do get better fuel mileage. But-have the ECU go out once and have to pay for a tow and repair bill-and all that savings go down the tubes. Give me mechanical any day. One of the many reasons I'm converting my '85 Kenworth-mechanical Cat 3406B. Not one electronic control on the whole truck. Good Luck, TomC

DDEC sounds great on paper and you do get better fuel mileage. But-have the ECU go out once and have to pay for a tow and repair bill-and all that savings go down the tubes. Give me mechanical any day. One of the many reasons I'm converting my '85 Kenworth-mechanical Cat 3406B. Not one electronic control on the whole truck.

Tom, you work with modern heavy trucks every day. How many ECUs are failing out in the field? I would guess that the vast majority of heavy trucks these days have electronic engines.

I would agree that for someone with mechanical skills a mechanical engine is going to be easier to fix. I'm just not convinced that ECUs fail that often. Modern cars are fully electronic and how often do you hear of an ECU failure on cars?

Tom, you work with modern heavy trucks every day. How many ECUs are failing out in the field? I would guess that the vast majority of heavy trucks these days have electronic engines.

I would agree that for someone with mechanical skills a mechanical engine is going to be easier to fix. I'm just not convinced that ECUs fail that often. Modern cars are fully electronic and how often do you hear of an ECU failure on cars?

Brian, I agree with you for new vehicles with factory installed engines, electronic systems, and associated components. But if I put an electronic engine in my bus, I'd be looking at a wiring harness, sensor components, grounds, electrical feeds, and a bunch of other stuff that I'd have to install. And the way that a lot of this stuff works is that if you have a bit more resistance than the ECM wants to see, or if you have a bad ground, or if a sensor wire comes loose, the whole system freaks out and -- if it doesn't stop you dead on the side of the road -- you're at least into "limp mode" or other such. I don't think that experience with factory systems is *anything* like we'd see trying to graft a full electronic engine/chassis system into one of our old buses.

Brian-it's not necessarily the ECU's failing-and they do-although as stated not that often. It's all the other ancillary systems attached to them. For instance-on the new Freightliners, there are 3 computers that have to talk to each other. If one goes down, lights start to flash, systems don't work, but usually the engine will still run. Have any of the sensors like-low coolant level, low oil pressure, high water temp, high oil temp, exhaust temp, cam position, exhaust cooler temp, DEF level indicator, DEF pump pressure, DEF heat, DPF (Diesel Particulate Filter) heat, DPF restriction, DPF fuel dosing, etc goes bad will either derate the engine or just plainly bring the truck to a stop. I quite frankly am surprised that the trucks and buses even get down the road. On top of this is the manditory ABS braking system, and the optional electronic traction control, optional roll over stability control, optional lane guidance, optional radar based collision avoidance system, reactive cruise control, passive cruise control. Then you have also all the electronic gauges, electronic controls on the air conditioning (two evaporators on a sleeper truck), and most wiring multiplexed (switches create an electronic sound [like a telephone] and the computer picks up that tone to turn that item on or off)-but did eliminate 141 wires under the dash. You need to be an electronics wiz to work on the modern truck/buses these days. The first thing the techs (no more mechanics) do is to hook up the lap top and see what's cooking. We have one mechanic just doing electrical trouble shooting. I'll keep with my mechanical controls. Good Luck, TomC

I think the advantages outweigh the negatives but only if the wiring is done by the book and in a professional manner. Seen a lot of hack wiring jobs in my day. Besides the pleasure of having things like cruise and diagnostics, a DDEC will automatically advance and retard timing so the smoke goes away. The project I am currently working on (DDEC II 6L71TA) has a sound far different from the old MUI. Just my 2 bits.

I'd do it if it were mine for the better mileage and other benefits, but I have worked with a lot of electronics on cars, so I'm not worried about some of the issues stated. Wiring should be first class though, with good grounding practices.